The risks associated with long-term use of postmenopausal hormone replacement agents are controversial. Insufficient research has been conducted to reliably estimate these risks. Further, major changes in the formulation of replacement therapies, as well as lack of clarity as to what constitutes "long-term" use associated with increased risk contribute to these uncertainties. In the past, attention focused on the increased risk of endometrial cancer associated with unopposed estrogen use in postmenopausal women. There have also been some reports that unopposed estrogen users have a slight, but consistent increased risk of breast cancer. However, recent reports of increased breast cancer risk associated with the use of progestational agents in postmenopausal women have underscored the fact that risks may also derive from this source. Volunteers for the Postmenopausal Estrogen/Progestin Interventions (PEPI) trial took active/placebo estrogen and progestin for the three years which constituted the active phase of this clinical trial. Given the issues summarized above, it is important to conduct a safety followup of the PEPI cohort. The primary safety issues related to use of replacement therapies are believed to be related to effects on the uterus and the breasts. Thus, to ensure that deleterious changes have not occurred, a three-year safety followup of the PEPI cohort will be conducted with the following objectives: 1. Obtain annual endometrial biopsies from PEPI participants for a period of three years. 2. Obtain annual mammograms from PEPI participants for a period of three years. 3. Evaluate the safety followup data.